Waterproof package for explosives



SERH NM* l. Mdm-1MM' 5N ,maman-3 I Aug 17 1965 G. GRIFFITH ETAL3,200,743

WATERPROOF PACKAGE FOR EXPLOSIVES Filed Oct. 24, 1965 In v e n 1 o r s:George L. Griffith Thomas E Dowlin United States Patent O 3,200,743WATERPROOF PACKAGE FOR EXPLOSIVES George L. Griffith, Coopersbnrg, andThomas P. Dowling, Fullerton, Pa., assignors to Trojan Powder Company,Allentown, Pa., a corporation Filed Oct. 24, 1963, Ser. No. 318,629 5Claims. (Cl. 102--24) This invention relates to low sensitiveexplosives, nitrocarbonates, and other explosives which have no inherentwater resistance and therefore lose usefulness if not packaged so as tobe completely water resistant and which must have a density when readyfor use suicient to allow the cartridge to sink in water but whichdensity should be lower than that at which the explosive would tend tolose sensitivity.

The principal object of this invention is to provide a container of suchmaterials as to furnish the stiffness and strength of conventionalspiral wound shells together with the ease by which it can be closed bysimple crimping and wax sealing and yet be completely water resistantalthough permitting normal methods of filling and use.

An important object of the invention is to provide a package of anammonium nitrate explosive which can readily be lled by auger loading.

A third object of the invention is to provide an inexpensive package oflow sensitive explosive which can be filled by auger loading, will beeffective under extreme heads of water pressure and have a densitygreater than land not over 1.15.

Many endeavors have been made to meet the requirements of an inexpensivepackage for explosives of the general type of prilled ammonium nitratewith a carbonaceous material and they have usually been successful inmost of the requirements, which are many, but each leave a desirablefeature only partially met, for example, many are too expensive, otherswithhold water but not for high heads or long immersions, others willnot sink in Water, while others have too great a density, some areperfectly waterproof but this feature is often lost in use or inloading, and others cannot support the expected loading pressures.

The requirements and difficulties are given in greater detail in thefollowing:

The use of either expandable tubing or non-expandable tubing such as aburlap outer tube with a polyethylene interior liner, or a conventionalspiral wound explosives shell, has a number ofdisadvantages-particularly when it comes to the less expensive ammoniumnitrate explosives. These disadvantages would also be present in similarpackages for explosives having little, if any, inherent waterresistance. We will discuss lirst the problems associated with thepackaging of nitrocarbonitrates.

Generally, all NCNs which do not contain non-explosive sensitizers suchas dinitrotoluene are completely desensitized by the addiition of evenvery minor amounts of water. It is possible to add water gelling agentssuch as Guar Gum and obtain some water resistance, but this is not onlyexpensive, but also would not be effective under extreme heads of Waterpressure.

Normally, also, any NCN which consists essentially of ammonium nitrateand a carbonaceous fuel becomes extremely insensitive if packaged to adensity above 1.15 It can readily be seen that to go to too high adensity results in poor sensitivity; to have a package which is notcornpletely water resistant likewise produces poor sensitivity. Theindustry consequently would like a total package which is waterresistant and not too dense.

Another problem is obtaining a total package which is relatively stiffand firm so that it can be loaded into ragged or crooked holes. Thebasic disadvantage of a plastic package is the fact that. it can veryeasily be cut or ruptured and essentially has little, if any, waterresistance after being handled in a normal manner.

An additional problem is obtaining suicient density to allow the packageto sink in water. This is extremely difiicult to do since about the onlyway one can obtain den sity is by bouncing or vibrating, because thepackage has no inherent strength and one cannot press or screw load it.

To get around the obvious disadvantages of the allplastic package,certain companies have put on the market a two-ply bag: the inner ply isa polyethylene tube, and surrounding this, there is a tube of` burlap,which in some instances is asphalt impregnated to give stiffness. Thispackage is difficult or impossible to load with any pressure or screwequipment since the screw (in the case of the polyethylene bag) can cutthrough the plastic bag and destroy its apparent water resistance. Also,since it has no stiffness, it cannot support any loading pressures otherthan conventional bumping or vibrating.

For a number of years the various explosives companies have put out anNCN package which is essentially a spirally wound tube with waterresistant or water impervious plies and with conventional closures whichare poured with hot wax to protect the contents. Tubes or shells such asthis can, of course, stand appreciable pressures and they can besatisfactorily loaded by pressing or by extrusion or vibration orbumping. However, even the best paper shell with the best possible endclosure is still not completely waterproof. Normally, it will stand somehydrostatic heads but field experience has definitely shown it will notstand appreciable heads of water for any long period of time.

To get around the disadvantages of the conventional explosive spiralwound shell, other companies have come out with a considerably heavierspiral Wound wall, which is dipped in hot asphalt or has a number ofmoisture vapor barrier plies which can be made essentially Waterprooffor a great period of time. To adequately prevent water from enteringeither end, metal ends have been seamed to the shell, and the industryhas essentially come up with a total package which is generallyextremely water resistant.

This type of package can, of course, be loaded in any manner whatsoeversince it has adequate strength in all respects. However, the metal endsare a disadvantage since they have a tendency to cut the cap leg wiresand also the Primacord, and furthermore they introduce metal into a borehole, which is not desirable; difficulties could be experienced withimpact and friction. This is particularly true since most holes loadedwith NCNs have some appreciable amounts of high explosives either forpriming or for pulling the bottom.

The most desirable package would be one which has all of the inherentstiffness characteristics of a conventional spiral wound shell,including its strength, its ease in closing by simple crimping and waxsealing, and also obviously it is the most economical type of container.However, as mentioned previously such a container is not waterresistant. It would seem rather simple to embody a polyolen plastic tubeinside of a spiral wound shell and to seal the polyethylene tubing byheat sealing or by wire tying, and come up with a completely waterproofpackage. A number of attempts have been made to do this, but they haveall presented a number of difficulties. First of all, when a spiralwound shell with a polyethylene inner tube is loaded by screwing, it isquite obvious the screw or auger can pierce or puncture the polyethylenetubing and destroy its water resistant characteristics. Also, if thematerial is extruded into the polyethylene tube, the extrusion pressuretends to force the polyethylene tubing down toward the bottom of thespiral wound shell. Essentially, one ends up with an accordion pleatedtube and in most instances it is not possible to avoid this. It might bepossible to have some method of holding the tube at the top of thespiral wound shell, but again, when the extrusion pressure is subjectedto the sides of the plastic tube there is a tensile force exerted on thetubing which can cause it to tear or rupture. Normally, pressureextruding is more expensive and more time consuming than screw loading.Screw loading or auger loading is the preferred method.

As thus shown, there are a number of problems associated with any of thepresent packages which are now being marketed-particularly for NCNs. Asimple, economical and practical package which will give all of thedesired characteristics and also all of the stiness characteristicsrequired is shown in the drawings in which the figure is a centralsection through a tubular package embodying the invention.

In the drawing the outer shell 10 is a conventional cylindrical body ofpaper spirally Wound into a firm shell having a radial thickness of froma twentieth to a tenth of an inch, preferably .060" to .090. Within theouter shell there is a polyethylene bag 12 of from three to twelve,preferably six, mil thickness loosely positioned between the shell andan inner tube 14, slightly shorter than the bag and like the shell alsoof spirally wound paper but only about .02 thickness, the clearancebetween the shell and the tube being about the same or slightly greaterthan the thickness of the inner tube. The bag may have a closed bottombut usually the bottom 16 will be closed by a suitable tie 17 or it maybe heat sealed. At the top the polyethylene bag may be suitably tied orotherwise closed and the open end of the outer shell is closed by simplecrimping and wax sealing as at 20.

The package thus produced is completely Water resistant and can beloaded by any conventional powder loading mechanism and it willwithstand any normal quarry handling and loading conditions.

What is claimed is:

1. In an explosive cartridge free of metal and closable by simplecrimping and wax sealing, a cylindrical body comprising an outercovering of paper spirally wound into a irm shell, a waterproof plasticbag within the shell, an inner tube of paper spirally wound to a radialthickness of less than the thickness of the outer shell and within saidbag, and a illing of low sensitivity ex plosive within the package andconined laterally by the tube, there being an annular space between theouter shell and the tube with a radial dimension of about .02" to allowlateral movement of the tube while loading the cartridge, said tubebeing of suicient strength to avoid injury to the bag as the cartridgeis loaded by conventional equipment, and being of a length less than thelength of the interior laoded portion of the bag.

2. The device of claim 1 in which the illing is of carbonaceous materialand ammonium nitrate.

J3. The cartridge of claim 1 in which the filling is a nitrocarbonitratewhich has a density of between 1.01 and 1.15.

4. The device of claim 1 in which the thickness of the outer shell isbetween .06" and .09, the waterproof plastic is a polyolein of athickness between three and twelve mils, the inner tube has a thicknessof at least .02 and the filling has no inherent water resistance.

5. In an explosive cartridge, a cylindrical body comprising an outercovering of paper spirally wound into a firm shell having a thicknessbetween .060" and .090", a waterproof plastic bag within the shell of athickness between five and nine mil, an inner tube of paper spirallywound to a radial thickness of between one-fifth and one-third of thethickness of the outer shell, a filling of nitrocarbonitrate within thepackage and confined laterally by the tube, there being an annular spacebetween the outer shell and the tube of roughly .02" in radialdimension, said space being occupied in part by said waterproof plasticbag, said tube being of sufficient strength to avoid injury to the bagas the cartridge is loaded by conventional screw or auger equipment, andsaid explosive cartridge being able to withstand appreciable heads ofwater for a long period of time.

References Cited bythe Examiner UNITED STATES PATENTS 2,513,531 7/50Taylor et al 102--24 2,754,755 7/56 Ruth et al. 102-24 2,887,954 5/59Swed 102-24 3,049,079 8/ 62 Eilo 102-24 3,095,335 6/ 63 McCloud et al.149-60 3,113,518 12/63 Doan 102-24 3,122,096 2/ 64 Wick 102-24 BENJAMINA. BORCHELT, Primary Examiner.

1. IN AN EXPLOSIVE CARTRIDGE FREE OF METAL AND CLOSABLE BY SIMPLECRIMPING AND WAX SEALING, A CYLINDRICAL BODY COMPRISING AN OUTERCOVERING OF PAPER SPIRALLY WOUND INTO A FIRM SHELL, A WATERPROOF PLASTICBAG WITHIN THE SHELL, AN INNER TUBE OF PAPER SPIRALLY WOUND TO A RADIALTHICKNESS OF LESS THAN THE THICKNESS OF THE OUTER SHELL AND WITHIN SAIDBAG, AND A FILLING OF LOW SENSITIVITY EXPOLISIVE WITHIN THE PACKAGE ANDCONFINED LATERALLY BY THE TUBE, THERE BEING AN ANNULAR SPACE BETWEEN THEOUTER SHELL AND THE TUBE WITH A RADIAL DIMENSION OF ABOUT .02" TO ALLOWLATERAL MOVEMENT OF THE TUBE WHILE LOADING THE CARTRIDGE, SAID TUBEBEING OF SUFFICIENT STRENGTH TO AVOID INJURY TO THE BAG AS THE CARTRIDGEIS LOADED BY CONVENTIONAL EQUIPMENT, AND BEING OF A LENGTH LESS THAN THELENGTH OF THE INTERIOR LAODED PORTION OF THE BAG.